The three primary approaches used to clean commercial and residential carpets are steam or hot water, foam and dry systems. Dry-type carpet cleaning systems are further divided into two broad categories, namely, those using a dry or substantially dry powder and those using granules which are slightly moistened with cleaning solvents for dirt removal. The invention has utility in both categories of dry systems but relates primarily to those using granules rather than powder. Such machine also has utility in situations where only carpet vacuuming is performed. That is, its aggressive, long-bristled brushes are highly effective in removing loose sand and other soil not requiring the application of solvent-bearing material.
Of the dry granular carpet cleaning systems, the best known and most widely used is the HOST.RTM. dry extraction system offered by Racine Industries, Inc. of Racine, Wis. The HOST.RTM. system applies granules to carpet fibers using a machine as shown in Rench et al. U.S. Pat. Nos. 2,842,788 and 2,961,673. Such machine, sold under the HOST.RTM. trademark, is devoid of vacuum capability and has a pair of spaced brushes counter-rotating at relatively low speed (about 350 rpm) to stroke the cleaning granules into, through and across carpet fibers. The granules are referred to as "dry" and are substantially so even though moistened with cleaning solvents. When stroked as described, these granules "scrub" soil and dirt from such fibers including oily and non-oily soil. The carpet is cleaned by working the HOST.RTM. machine across it in different directions. During the clearing process, granules migrate to the carpet backing adjacent the base of the fiber. A few granules also adhere lightly to the fibers along their lengths. Following cleaning, conventional carpet vacuum machines are used for removing the dirt-ladened granules.
Because of the way they are constructed, conventional vacuum machines are not ideally suited for the removal of such dirt-ladened granules although such machines do a reasonably acceptable job of such removal. In particular, most such machines employ a single "beater bar" which rotates at high speed and which uses spaced rows of relatively short bristles. A few such machines have two beater bars which are constructed and operate in much the same way. Such high speed beater bars with short bristles are more effective in removing granules near the tops of the fibers but significantly less so as to granules which are "deep down" in the carpet.
In such conventional machines, it is not possible to apply the beater bar alone to the carpet, i.e., to use such bar with the vacuum nozzle raised above the carpet. In other words, the beater bar and the vacuum nozzle are used simultaneously to clean the carpet.
Another disadvantage of such machines is that the beater bars are driven by smooth-surfaced, flexible rubber belts which wrap partially around the bar. The solvent used to moisten the granules often causes the belt to slip, thereby temporarily disabling the beater bar.
Further, the embodiment of carpet brushing and carpet vacuuming capabilities in two separate machines means that two separate machines must be available to complete the cleaning process. This represents an extra equipment expense and for the professional carpet cleaner, it also represents added time (reflected in employee wages) required to get the necessary machines to the job site and to later remove such machines.
One type cf carpet machine is shown in Smellie U.S. Pat. No. 1,891,504. The Smellie machine uses two counter-revolving bars, commonly known as "beater bars," each having two elongate brushes. For each bar, the two brushes thereon are positioned about 180.degree. apart and are arranged in a gentle spiral. Each brush is shrouded over its entire length and over about 90.degree. of its circumference. An elongate vacuum inlet is positioned adjacent the perimeter of each brush and dirt extracted from the carpet by the brushes is drawn into these vacuum inlets and thence to a dust collector. The Smellie machine is constructed such that the nozzle lips and the brushes are simultaneously brought into contact with or moved away from the surface of the carpet being cleaned.
The vacuum cleaner shown in the Riebel, Jr. U.S. Pat. No. 2,064,856 and Riebel, Jr. et al. U.S. Pat. No. 2,064,852 employs a single beater bar on which is alternately mounted brush elements and beaters. Vacuum inlets are defined on either side of the beater bar. The machine is depicted to draw a carpet up against the vacuum nozzle where it is struck by the beater bar. Presumably, dust and dirt are thereby removed. As with the Smellie cleaner, the vacuum nozzle and the beater bar must move simultaneously to contact the carpet or be removed therefrom. Somewhat similar carpet vacuuming machines are shown in Nordeen U.S. Pat. No. 4,426,751 and Dufour U.S. Pat. No. 664,135.
Notwithstanding the efficacy of these earlier machines, they do not address the particular requirements arising from the application of dry cleaning granules to a carpet and subsequently removing such granules using the same machine. In particular, application of such granules requires that the machine brushes be free to engage and distribute a mound of cleaning granules as such granules are worked into the carpet and across the carpet fibers. Granule redistribution, important for uniform cleaning, is aided by having a significant space between the carpet and the machine shroud so that granules thrown about by the brushes are redistributed upon the carpet in many directions.
On the other hand, removal of these granules from the carpet by vacuuming is very effectively accomplished by a machine which can be closely "fitted" to the carpet surface, thereby forcing high-velocity, granule-entraining air to be drawn through the carpet fibers and upward into the vacuum inlet for improved granule removal. Earlier workers in this field did not appreciate how these two seemingly inconsistent requirements may be met by a single machine.
An improved carpet cleaning machine having a shroud with edges spaced from the carpet during the application of dry cleaning granules and a movable skirt disposed around such edges for closing these spaces when removing granules by vacuuming would be an important advance in the art.